1. Field of the Invention
The present invention relates to a spacer disposed between a vehicle brake drum and wheel. More particularly, the present invention relates to a wheel spacer disposed between a vehicle wheel and brake drum having thermal insulating properties.
2. Description of the Prior Art
Various prior art methods have been employed to effectively lower the operating temperature of a vehicle wheel and tire assembly to improve service life. A variety of fins and/or channels formed in the surfaces of the wheel and/or brake drum to promote airflow have been devised as a method to increase the rate of thermal convection from the surface of the wheel and/or brake drum into the surrounding air. Examples of these prior art methods can be seen by reference to U.S. Pat. Nos. 2,055,244; 2,998,870; 3,090,114; and 4,536,936, the disclosures of which are hereby incorporated by reference. The purpose of these prior art devices is ultimately to decrease the operating temperature of either the brake drum and/or the vehicle tire to promote longevity when operating in extreme environments. The frictional heating of the brake drum by the brake shoes causes an extreme amount of heat to be transferred not only by convection into the surrounding air but also by conduction through the brake drum flange into the wheel hub and ultimately into the tire. An extreme amount of heat transferred into the tire can cause transformation of the rubber primarily at the wheel/tire interface in an area known as the tire bead. This transformation breaks down the rubber compounds resulting in a shortened service life and possible failure due to air loss at the tire bead.
Many types of prior art air channels and cooling fins have been somewhat effective in an attempt to lower operating temperatures of both the brake drum and/or the wheel/tire. However, none of the prior art devices have been proved entirely satisfactory due to increased costs, complicated fabrication or involved casting processes and/or limited control of heat build-up due to ineffective promotion of airflow.